Movable conveyor bridges are used for conveying material, for example from the site of a mining operation. A problem exists in moving a conveyor bridge over uneven ground without introducing the forces that result from the unevenness of the ground to the conveyor bridge. This is especially a problem in oil sand or tar sand mines and in many different applications. This is particularly difficult on side slopes or uphill sections since the conveyor bridge must always be directed horizontally (in the lateral direction) to make it possible to convey material.
A conventional technique to control the level of the conveyor bridge is to provide a tilting joint in the longitudinal direction having a tilt axis at a right angle to the conveyor bridge. The tilting joint is provided above the swivel joint. Another tilting joint in the transverse direction is provided below the swivel joint. This other tilting joint has a tilt axis along the conveyor bridge. This arrangement disadvantageously leads to the drawback that the conveyor bridge can only be kept horizontal when the chassis is at right angles (90°) to the conveyor bridge. As such, keeping the conveyor bridge horizontal at other steering positions is very limited. This makes it difficult to maneuver the conveyor bridge along uneven or sloped ground. Further, such a conventional technique can only be used where even and well prepared ground conditions are present, such as in leach pad systems. There are other well prepared surface applications other than leach pad systems. Leach pad systems are ore extraction systems used in the copper and gold industry in which finely crushed ore is loaded on a pile over a large area and irrigated with an acid solution. Over time the ore is leached out of the rock. The leach solution is then collected and the mineral in the leach solution is extracted. Leach pads have well prepared ground conditions which are flat and horizontal. As such, the conventional techniques used for leach pad systems are not suited for applications where movable conveyor bridges have to travel about uneven ground conditions, such as sand oil or tar sand mines in which the ground is uneven and sloped since a cylinder arrangement having a greater path of adjustment is necessary to maintain the conveyor bridge in a stable position. Accordingly, there exists a need to solve the problem of maintaining a conveyor bridge in a horizontal position when the conveyor bridge is moved along uneven ground or located on a sloped section of ground.
U.S. Pat. No. 5,404,988 (corresponding to DE 42 05 557) discloses a connecting belt bridge provided with the feed end side and the discharge side end each supported on respective traveling means. The discharge side traveling means includes a traveling unit which is not railbound. The connecting belt bridge is pivotally supported on the discharge side traveling means by way of a ball joint connection and on the feed side traveling means by a longitudinally displaceable single point support including a support beam which can be horizontally aligned and has at its feed side end a feed jib hinged on by way of a horizontal transverse axis. However, the connection to the traveling means with this type of joint does not fully address the problem regarding supporting a polynominal conveyor bridge that is supported by several self-propelled chassis and moving across ground that is uneven and sloped.